Heat resistant transparent laminate



Ufliifd Sims tentO HEAT RESISTANT TRANSPARENT LAMINATE iluther '-L. Yaeger, Madison, 'Wis., assignor to Bjorksten Research Laboratories, Inc., a corporation of Illinois No Drawing. Applicationfl'ctober 31, 1952, Serial No. 318,071

1 Claim. (Cl. 154- 175 This invention relates to a laminate: comprising substantially rigid transparent sheets having an interlayer laminated thereinbetweencomprising-the polymeric con- 2,789,932 Patented Apr. 23, 19 5? Example 1 A surface of each of two glass sheets was sprayed with a 'soluti'on'in methyl ethyl ketone of an epoxy resin having the following formula:

densation product of terephthalic acid and ethylene glycol.

Heretofore it has been the practice to laminate glass or acrylic resin sheets with an interl'ayer comprising a resin such as polyvinylacetal, a celluloserester,;.polyamides, and the like. Such laminates have several important disadvantages. They tend to degradate at :high temperatures, to become inelastic atlow temperatures and to be insutficiently transparent or to become insufiiciently transparent after a period of time or after being .subiected to temperature extremes.

Temperatures generated by air resistance in aircraft glazing members, such as Windshields, during the operation of supersonic aircraft reach very high values and Isuch members are also subjected to extremely low temperatures due :to operation under arctic conditions and at extremely high altitudes. High temperatures are also attained in the Windshields of aircraft which are heated to prevent the formation of ice thereon.

It is therefore desirable that transparent laminates retain certain physical properties at a temperature of 400 F. and that the resinous interlayer not become degraded by heating for as much as two hours at 400 F. The physical properties referred to include the property of the laminate to resist delamination when struck by a bullet, the propertyof Ethe interlayer to "se l f.-seal--or :to substantially selfseal the hole left by a bullet passing through the laminate, a high .degree of light transmission which should preferably be greater than 87% and at the same time a minimum of haze which should be less than 3%. An article is translucent which merely transmits a high percentage of :light but at athe same time is =-hazy and therefore it may be seen that the quality of transparency involves both %the amount of flight transmission and degree ofhaze. The 'same properties should be retained at temperatures down to ancl'below 65 F.

It is therefore'an object'of this invention to'provide a laminate interlayer having superior retention "of desirable physical properties 'at extreme temperatures.

It is another object 'to provi'de a "laminate having superior physical properties at extreme temperatures.

. It is another'objectto'provitle such 'alaminate comprising glass or synthetic resin Isheetsihaving ilaminated thereain'between an interlayer :comprising a :polyester synthetic resin.

Another object is a glass laminate provided with an yer comprisi a po ymer f ethy ene sl'yc an terephthalic acid.

Further objects will become apparent from the following detailed description in which it is my intention to illustrate the applicability of the invention without limiting its scope to less than that of all equivalents.

wherein R may be O- or where Y is-CzHze-iiand'x is- 1 to Miami "Rand also at '6'S F. when clamped 'in a"te'st, chamber pressurized with 6 p. s. i of air and fractured bullpt penetration was outstanding.

Example '2 A sandwich of glass plates and ethylene glycol-tereph- .thali acidpolym w t a p y e n as an adh was prepared as in :Example 1. The .-sandwlch was cured between steel platens at 425 F. under "300 p. s. 'i. for T5 minutes; excessive adhesive'fiowed out of 't'he'laniinattes; when cool the :following optical properties were obtained:

ercen Light transmission 92.2 Haze? v The laminate was reheated to 400 F. for two .hours to simulate -.the .eff ectof use as-a windshieldin.fastetlying aircraft. The adhesive and interlayer .did :not .discolor or delaminate and the optical-properties after. such .treatmen; were found tobe:

Percent Light transmission t.--" 90.8 Haze 1 .5

This laminate while at a temperature of 400 'F; and

also .while .at .a temperature of +65 was clamped s sk yinto a Window el a enclosed test hen ll 6 p. s. i. air pressure was applied to "the chaniber'and'the window was punctured by bullet penetration. No shat tering of the laminate occurred at either temperature.

Example 3 duced with interlayers of other polymeric materials. The epoxy resin Sold commercially as Epon Laminates comprising filmslaminated between glass plates which has the following formul were checked for visual light transmission, heated for C :CH-CHi-O --R- O CH2-(|3H-CH2O R O CHE-"C CHI 0 H I a whereinRmay be O- or two hours in a ventilated oven at 400 F. and the optical Y properties were again measured. INITIAL PROPERTIES I Y Plolyetthylenle Tirasngpar- Pgbglhiolo- Mlodifiel Clgosls-llnkeld L aye erep en cone ri uoro no yami e o yviny where Y CIHZH and x 13 1 6 and thalate (2 mi Elastomer ethylene 7 mil film) butyral film) (25 mil film) (6 mil film) (25 mils) 92 85 91.5 01 90 is bis-phenyl which may be halogen substituted, and has 23 A I an average molecular weight of .69, was combined with i g a catalyst and used in place of the epoxy resin adhesive of PROPERTIES AFTER 2 AT example 1 and similar results were obtained. Triethylamine was used as the catalyst but other catalysts and 1 80 9M gfg gg gggg gf gg fiactivators known to the art, selected from the groups conm I 0 sisting of multicarboxylic acids and polyfunctional amines have been used and found suitable. 1 Light transmission (percent).

'-' Haze (percent).

Example 4 I It will thus be seen that my invention is broad 111 scope The process of example 3 was repeated with a similar d i not to b li i d except b h l i epoxy resin having an average molecular Weight of ap- I l i pfoxlmately 355 Sold commerclauy by Shell p- A transparent laminated safety glass article compris- F p y P Q and W38 80 repeated irig two sheets of glass; a layer of the polymeric condensa- With an p y resin having an average molecular welght tion product of terephthalic acid and ethylene glycol 05 apploxlmately 710 Sold commefclally y Shell 3 laminated thereinbetween, and as an adhesive between velopment Company as Epoii RN1064. said layer and each of said sheets of glass, a layer of a In both cases similar superior results were obtained. resin having the following formula:

' 0 I I o CHRCHCH:O R- o- -CH'.(,JHCHi-0 iz- -o]cni-o ---CH! Example 5 wherein R may be --0 or Laminates were prepared as in examples 1 to 5, using 5 j. sheets of polymethylmethacrylate in place of glass. The Y resulting laminates exhibited difierences in physical prop- -6.

erties due to the use of polymethylmethacrylate rather 1 I than glass, but similar superior results were obtained Y with each of the laminates. 5

whereYisczHzzuandxisltofiand M Example 6 v A film of the polymeric condensation product of tereph- Ithalic acid and ethylene glycol .003 in thickness was O I laminated between two sheets of glass at a temperature 5 of 375 F. and a pressure of 200 to 300 p. s. i. The glass sheets were cleaned prior to lamination but were not is bis-phenyl which may be halogen substituted; coated with any adhesive or bonding agent such as an epoxy resin, as was the ease with the other laminates. References-Cm! 1n the file of this Pam!t Ilie laminate thus produced resisted degradation of the v U STATES PATENTS interlayer and exhibited the same retention of trans 1,899,588 RO-hIfS Feb. 28, 1933 parency at high and low temperature extremes as was 2,465,319 Whinfield Mar. 22, 1949 the case with the laminates of examples 1 to 5, but ex- 2 591 539 Greenlee A r 1 1952 =hibited a substantially greater tendency to delaminate 265O213 H ofrichte; 1953 when struck by a bullet.

The conditions under which the laminate may be pre- OTHER REFERENCES pared are generally not critical. Generally the laminate 1 m be made by heating at to for from Araldite, l3rit. Plastics,; November 1948, pp. 521-525. ,5 minutes to 45 hours at a pressure of from 2 to 10,000 EPOI1 Refills, Palm, 011 and chem- Novembfl p. s. i. 1 9, 1950, vol. 113, issue No. 23, pp. 15, 18, 48, 49. The ,superiorityof the laminate produced in accord- Epon Resins for-Laminating, Technical Bulletin- 8. C.

'ance with'thisinvention may be observed from the fol- 52-6 of Sliell'Chem. Corp., March 1952, 5. 1. lowinjgQtable which presents a comparison of a laminate produced according to this invention with laminates pro- 

